BAGHDAD -- Militant Shiite cleric Muqtada al-Sadr called Tuesday for followers to hold weekly protests against a U.S.-Iraqi security deal under negotiation that could lead to a long-term American troop presence.
The outcry by al-Sadr could heighten tensions over the proposed pact, which is supposed to be finished by July to replace the current U.N. mandate overseeing U.S.-led troops in Iraq.
Al-Sadr -- whose powerful Mahdi Army militia has often battled U.S. and Iraqi forces -- is one of the most vocal opponents of the U.S. presence in Iraq, but many Iraqis have expressed worries over any final deal that involves permanent American bases.
Al-Sadr, who is believed to be in Iran, did not give specific guidance on the planned demonstrations.
Any major marches, however, could put added strain on a tenuous truce between the Mahdi Army and the government of Prime Minister Nouri al-Maliki after weeks of battles that began in late March.
In northern Iraq, meanwhile, a car bomb exploded near a popular market in Tal Afar, killing four civilians and wounding 46 others, said the city's mayor, Maj. Gen. Najim Abdullah.
There was no immediate claim of responsibility. It came hours after an al-Qaida in Iraq front group warned that insurgents would retaliate against U.S. and Iraqi forces, which began a crackdown nearly two weeks ago in the main northern city of Mosul, 40 miles east of Tal Afar.
A man claiming to be a spokesman for the Islamic State of Iraq in Ninevah province, which includes Mosul, said in a videotape posted online that insurgents were at "full strength" despite the Mosul sweeps and were just waiting for the proper time to counterattack.
"We are the ones who control the hour to start the initiative and we will choose the time for retaliation or engagement," said the unidentified spokesman, whose face was covered. The Islamic State of Iraq is a coalition of insurgent groups lead by al-Qaida in Iraq.
There was no way to authenticate the comments. But the video bore the logo of al-Furqan, one of al-Qaida's media production wings, and was posted on a number of Islamic Web sites that usually carry militant statements.
Mosul, 225 miles northwest of Baghdad, has been dubbed by the U.S. military as al-Qaida's last major urban stronghold in Iraq.
Officials have claimed initial success in the crackdown, saying more than 1,200 suspects have been detained. Iraqi security forces also have met with little resistance -- though there have some attacks, including a shooting near a Mosul police station that killed one policeman Tuesday, according to Interior Ministry spokesman Maj. Gen. Abdul-Karim Khalaf.
On the political front, al-Maliki convened a meeting with Iraq's president, the two vice presidents and other political leaders late Monday to discuss the ongoing negotiations with the U.S. over a security deal.
The prime minister said the decision "should shared by all political powers in the country," said Nasser al-Ani, a spokesman for the presidential council. He said the delegates agreed to continue the dialogue.
Details of the terms under negotiation are not known. Al-Maliki has said the agreement will provide for U.S. security help to protect Iraq, and most Iraqi leaders have said they support some form of continued American role. But the numbers of American troops and the rules of conduct in Iraq remain highly controversial.
Al-Sadr's statement urged Iraqis across the country to hold demonstrations every week after Friday prayers "until further notice or until the agreement is canceled." He urged politicians from all factions to work against the agreement.
He also demanded that any agreement reached with the Americans be put to a popular referendum. He vowed to gather 1 million signatures rejecting the deal.
In the capital, al-Maliki and a host of political and religious figures inaugurated a rebuilt bridge linking east and west Baghdad that was destroyed more than a year ago by a suicide truck bomber. The April 2007 bombing sent sections of the al-Sarafiyah bridge plunging into the Tigris, killing at least 10 people.
The U.S. military said an American soldier was killed and two others were wounded Sunday in a roadside bombing in a mostly Shiite area 110 miles south of Baghdad.
In Stockholm, Sweden, Prime Minister Fredrik Reinfeldt urged the United States and European countries to admit more Iraqi refugees.
Sweden, which opposed the U.S.-led invasion of Iraq, has received about 40,000 Iraqis since 2003. The United States admitted just over 1,600 Iraqi refugees in the 2007 fiscal year which ended Sept. 30, but the Bush administration seeks to bring in 12,000 Iraqi refugees by the end of September this year.
The pace, however, has been slow and suggests Washington could fall far short of the goal unless the refugee flow is sharply increased.
Reinfeldt is hosting a conference Thursday on Iraqi development. Among those scheduled to attend include Secretary of State Condoleezza Rice, U.N. Secretary-General Ban Ki-moon and the Iraqi prime minister.
Associated Press writers Hamid Ahmed in Baghdad and Maamoun Youssef in Cairo, Egypt, contributed to this report.